package bishi2016;

import java.util.*;

public class MoGuJie_MoveRound {

	//这道题的关键就是只要圆心坐标与移动后的圆心坐标之间的距离在[0, 2 * r]，就可以通过一次移动来到达想要的圆心坐标
	public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);
		long x, y, x1, y1, r;
		double distance;
		while (scanner.hasNext()) {
			r = scanner.nextInt();
			x = scanner.nextInt();
			y = scanner.nextInt();
			x1 = scanner.nextInt();
			y1 = scanner.nextInt();
			distance = Math.sqrt((x - x1) * (x - x1) + (y - y1) * (y - y1));
			// 不要输出小数点
			System.out.printf("%.0f\n", Math.ceil(distance / (2 * r)));
		}
		scanner.close();
	}
}
